Mounted body and method for manufacturing the same

ABSTRACT

A mounted body ( 100 ) of the present invention includes: a semiconductor element ( 10 ) having a surface ( 10   a ) on which element electrodes ( 12 ) are formed and a rear surface ( 10   b ) opposing the surface ( 10   a ); and a mounting board ( 30 ) on which wiring patterns ( 35 ) each having an electrode terminal ( 32 ) are formed. The rear surface ( 10   b ) of the semiconductor element ( 10 ) is in contact with the mounting board ( 30 ), and the element electrodes ( 12 ) of the semiconductor element ( 10 ) are connected electrically to the electrode terminals ( 32 ) of the wiring pattern ( 35 ) formed on the mounting board ( 30 ) via solder connectors ( 20 ) formed of solder particles assembled into a bridge shape. With this configuration, fine pitch connection between the element electrodes of the semiconductor element and the electrode terminals of the mounting board becomes possible.

This application is a division of U.S. Ser. No. 11/911,144, filed Oct.10, 2007, which is a U.S. National Stage Application ofPCT/JP2006/303037, filed Feb. 21, 2006, which applications areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to a mounted body and a methodfor manufacturing the same. In particular, the present invention relatesto a mounted body in which a semiconductor element is mounted on amounting board and a method for manufacturing the same.

BACKGROUND ART

Accompanying the miniaturization and performance enhancement ofelectronic equipment in recent years, the number of pins in asemiconductor element included in the electronic equipment increases andvarious types of electronic components constituting the electronicequipment become smaller. Accordingly, there has been a dramaticincrease in the number and density of wirings in a printed board onwhich they are mounted. In particular, the number of leads led out fromthe semiconductor element (semiconductor chip) and the number ofterminals have increased rapidly, so that the printed board (wiringboard) becomes increasingly finer. Consequently, fine pitch connectiontechniques are gaining greater importance.

The fine pitch connection techniques can be divided broadly into a wirebonding (WB) method, a flip chip bonding (FC) method, and a tapeautomated bonding (TAB) method, each of which will be described brieflyin the following.

According to the wire bonding (WB) method, electrodes of a semiconductorchip and electrodes of a lead frame are connected to each other mainlyusing gold wires (diameter: 20 to 25 (m). The connection is achievedthrough solid phase diffusion caused by applying heat or ultrasonicwaves to the gold wires and the electrodes of both the semiconductorchip and the lead frame. The WB method is disclosed in Patent Document1, for example. According to the flip chip bonding (FC) method, bumps(protruding electrodes) are formed on a semiconductor chip, and thesebumps are connected to electrodes on a wiring board. The FC method ischaracterized in that it provides a configuration in which a surface onwhich the electrodes are formed (hereinafter, referred to simply as an“electrode-formed surface”) of the semiconductor chip and anelectrode-formed surface of the wiring board face each other. The FCmethod is disclosed in Patent Document 2, for example. According to theTAB method, semiconductor chips first are connected to a long tapeprovided with lead wirings. The chip provided with the lead then ispunched out from the tape, and the lead is connected to a substrate.Basically, the TAB method is carried out automatically through areel-to-reel process. The TAB method is disclosed in Patent Document 3,for example.

-   -   Patent Document 1: JP 4 (1992)-286134 A    -   Patent Document 2: JP 2000-36504 A    -   Patent Document 3: JP 8 (1996)-88245 A

The WB method disclosed in Patent Document 1 will be described withreference to FIGS. 21A and 21B. FIG. 21A is a top view showing thewire-bonded state, and FIG. 21B is a cross-sectional view taken along aline I-I in FIG. 21A

According to the WB method, a semiconductor chip 501 is die-bonded to aportion (a die pad) of a lead frame 504, and then wire bonding pads 502of the semiconductor chip 501 and external terminals 505 (inner leadportions) of the lead frame 504 are wire-bonded using bonding wires 503.Thereafter, a region including the semiconductor chip 501 and the innerlead portions of the external terminals 505 is encapsulated with anencapsulation resin 506, whereby, for example, a resin-encapsulated body(a semiconductor module) 500 as shown in FIG. 22 is obtained. Theexternal terminals 505 exposed from the encapsulation resin 506 areconnected to a wiring board (not shown), whereby the semiconductor chip501 is connected electrically to the wiring board.

However, the WB method has the following problems. First, there is aproblem in that a mounting area of a semiconductor element component(here, this refers to the module 500 including the semiconductor chip501) is large. That is, in the WB method, since the semiconductor chip501 is not mounted on the wiring board directly but is connected to theexternal terminals 505 of the lead frame 504 via the bonding wires 503,it is inevitable that the size of the semiconductor module 500 (theelement size or the component side) becomes larger than that of thesemiconductor chip 501. Consequently, the mounting area of thesemiconductor module 500 becomes large.

Furthermore, since the wire bonding pads 502 of the semiconductor chip501 and the external terminals 505 of the lead frame 504 are connectedto each other one by one with the bonding wires 503, there is a problemin that, as the number of the terminals increases, the time and effortrequired for the operation increase. Moreover, the pitch of the externalterminals 505 on the lead frame 504 defines the pitch of thesemiconductor element 500, thus imposing limitations on the narrowing ofthe pitch.

Next, the FC method disclosed in Patent Document 2 will be describedwith reference to FIG. 23. FIG. 23 shows a cross-sectional configurationof a semiconductor device 600 mounted by the FC method.

According to the FC method, electrodes 604 of a semiconductor chip 605are connected to wiring patterns 602 provided on a substrate 601 viabumps 603. More specifically, the electrodes 604 of the semiconductorchip 605 that has a sensitive area 606 in which a transistor etc. areformed are connected to the predetermined wiring patterns 602 providedon the substrate 601 via the bumps 603, whereby the semiconductor chip605 is mounted on the substrate 601 with a space being formedtherebetween. Thereafter, an encapsulation resin 607 is formed byinserting resin into the space between the substrate 601 and thesemiconductor chip 605 so as to embed the wiring patterns 602, the bumps603, and the electrodes 604 in the resin. The semiconductor device 600for which the FC method is employed is configured as above.

However, the FC method has the following problems. First, there is aproblem in that aligning the semiconductor chip 605 is difficult.According to the FC method, since the semiconductor chip 605 is mountedon the substrate 601 with its electrode-formed surface facing downward,the bumps 603 of the semiconductor chip 605 cannot be seen directly fromthe outside. This makes the alignment very difficult. Moreover, thepitch of the electrodes 604 of the semiconductor chip 605 when the FCmethod is employed is narrower than the pitch of the external terminals505 when the WB method is employed. This factor also makes the alignmentdifficult.

Also, there is a problem in that the substrate 601 is liable to beexpensive. The reason for this is that, according to the FC method, thesubstrate 601 is required to have the wiring patterns 602 that are finepatterns corresponding to the pitch of the electrodes 604 of thesemiconductor chip 605. Another reason is that, when the electrodes 604of the semiconductor chip 605 are arranged in an area array form, thesubstrate 601 is liable to have a multilayer structure. Moreover, whenthe FC method is employed, the semiconductor chip 605 is connected tothe substrate 601 via the bumps 603. Thus, unless the coefficient oflinear expansion of the semiconductor chip 605 is made as close aspossible to the coefficient of linear expansion of the substrate 601, astress is applied to the bumps 603 etc. Therefore, it is necessary tomatch the coefficients of linear expansion of both the semiconductorchip 605 and the substrate 601, and the matching of the coefficients oflinear expansion needs to be performed strictly. In this respect, thecost of the substrate 601 increases.

Moreover, since the semiconductor chip 605 is connected to the substrate601 via the bumps 603, the heat dissipation is deteriorated. Morespecifically, since the semiconductor chip 605 is disposed on thesubstrate 601 with points thereof being in contact with the substrate601 rather than the surface thereof being in contact with the substrateas in the case of the WB method, the heat dissipation is deteriorated.Also, in the first place, forming the bumps 603 takes time and effort.

Next, the TAB method disclosed in Patent Document 3 will be describedwith reference to FIGS. 24 and 25. FIG. 24 shows a cross-sectionalconfiguration of a semiconductor device 700 for which the TAB method isemployed, and FIG. 25 shows a configuration in which this semiconductordevice 700 is mounted on a mounting board 709.

The semiconductor device 700 shown in FIG. 24 includes a base film 702of a film carrier tape and a semiconductor IC chip 701 arranged in adevice hole 702 b provided in the base film 702. Copper foil wirings 703are formed on the base film 702, and electrodes 701 a of thesemiconductor IC chip 701 are connected to inner leads 703 a provided ininner end portions of the copper foil wirings 703. Lands 703 b forexternal connection are provided at portions of the copper foil wirings703 on the outer side relative to the inner leads 703 a, and solderbumps 706 are formed on the lands 703 b. Through holes 702 a areprovided in the base film 702. At the center of each of the lands 703 b,a pore 703 c is provided. A cover resist 704 is formed on the filmcarrier tape excluding the portions where the lands 703 b are formed. Anencapsulation resin 705 for protecting the semiconductor IC chip 701 isprovided in the device hole 702 b.

In this semiconductor device 700, the solder bumps 706 serve as outerleads, and as shown in FIG. 25, the solder bumps 706 are connected topads 709 a on the mounting board 709. The semiconductor device 700 forwhich the TAB method is employed is mounted on the mounting board 709 bya mass reflow process.

However, the TAB method has the following problems. First, since aninner lead bonding (ILB) step and an outer lead bonding (OLB) step areseparate steps, it takes time and effort to perform the TAB method. Morespecifically, in the example shown in FIG. 24, the step of connectingthe inner leads 703 a to the electrodes 701 a of the semiconductor ICchip 701 and the step of forming the solder bumps 706 at the lands 703 bare different types of steps, which complicates the operation.Furthermore, it is also necessary to encapsulate the semiconductor ICchip 701 arranged in the device hole 702 b with the encapsulation resin705, which also takes time and effort. In addition, there is a differenttype of problem in that, because the base film 702 having a larger areathan the semiconductor IC chip 701 is used, the mounting area increases.

DISCLOSURE OF INVENTION

The present invention has been made in light of the above-describedproblems. The present invention provides a mounted body for which anovel fine pitch connection technique that is different from the wirebonding (WB) method, the flip chip bonding (FC) method, and the tapeautomated bonding (TAB) method is employed and also provides a methodfor manufacturing the same.

A mounted body according to the present invention includes: asemiconductor element having a surface on which an element electrode isformed and a rear surface opposing said surface; and a mounting board onwhich a wiring pattern having an electrode terminal is formed. The rearsurface of the semiconductor element is in contact with the mountingboard, and the element electrode of the semiconductor element isconnected electrically to the electrode terminal of the wiring patternformed on the mounting board via a solder connector formed of solderparticles assembled into a bridge shape.

A method for manufacturing a mounted body according to the presentinvention includes the steps of: (a) placing, on a mounting board onwhich a wiring pattern having an electrode terminal is formed, asemiconductor element having a surface on which an element electrode isformed and a rear surface opposing said surface such that the rearsurface of the semiconductor element faces the mounting board; (b)applying a solder resin paste, obtained by mixing in a resin a solderpowder and a convection additive that boils when the resin is heated, toa region including the element electrode and the electrode terminal; (c)arranging a substrate having a first surface on which an electrodepattern is formed and a second surface opposing the first surface suchthat the first surface of the substrate faces the surface of thesemiconductor element and the mounting board with the solder resin pasteintervening therebetween and that the electrode pattern of the substratecovers the element electrode and the electrode terminal; and (d) heatingthe solder resin paste so that the convection additive boils to causeconvection in the resin, thus causing self-assembly of the solder powdercontained in the solder resin paste to form a solder member thatconnects at least between the element electrode and the electrodepattern and between the electrode terminal and the electrode pattern.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view schematically showing the configurationof a mounted body according to Embodiment 1 of the present invention.

FIG. 2 is a plan view schematically showing the configuration of themounted body according to Embodiment 1 of the present invention.

FIGS. 3A to 3E are cross-sectional views illustrating major steps in amethod for manufacturing the mounted body according to Embodiment 1 ofthe present invention.

FIG. 4 is a cross-sectional view schematically showing a mounted bodyaccording to Embodiment 2 of the present invention.

FIG. 5 is a cross-sectional view schematically showing a mounted bodyaccording to Embodiment 3 of the present invention.

FIG. 6A is a cross-sectional view schematically showing an applicationexample of the mounted body according to Embodiment 3 of the presentinvention, FIG. 6B is a view showing the planar configuration of anelectrode pattern in this mounted body, and FIG. 6C is a view showingthe planar configuration of another electrode pattern 42 in this mountedbody.

FIG. 7 is a cross-sectional view schematically showing a mounted bodyaccording to Embodiment 4 of the present invention.

FIG. 8 is a cross-sectional view schematically showing an applicationexample of the mounted body according to Embodiment 4 of the presentinvention.

FIG. 9 is a cross-sectional view schematically showing anotherapplication example of the mounted body according to Embodiment 4 of thepresent invention.

FIG. 10 is a cross-sectional view schematically showing still anotherapplication example of the mounted body according to Embodiment 4 of thepresent invention.

FIG. 11 is a cross-sectional view schematically showing a mounted bodyaccording to Embodiment 5 of the present invention.

FIG. 12 is a cross-sectional view schematically showing a mounted bodyaccording to Embodiment 6 of the present invention.

FIG. 13 is a cross-sectional view schematically showing an applicationexample of the mounted body according to Embodiment 6 of the presentinvention.

FIG. 14 is a cross-sectional view schematically showing anotherapplication example of the mounted body according to Embodiment 6 of thepresent invention.

FIGS. 15A to 15E are cross-sectional views illustrating major steps in amethod for manufacturing the mounted body according to Embodiment 6 ofthe present invention.

FIG. 16 is a cross-sectional view schematically showing still anotherapplication example of the mounted body according to Embodiment 6 of thepresent invention.

FIG. 17 is a cross-sectional view schematically showing still anotherapplication example of the mounted body according to Embodiment 6 of thepresent invention.

FIG. 18 is a plan view schematically showing still another applicationexample of the mounted body according to Embodiment 6 of the presentinvention.

FIG. 19 is a cross-sectional micrograph for illustrating the state ofsolder connectors formed in a self-assembled manner in a mounted bodyaccording to Embodiment 7 of the present invention.

FIG. 20 is a cross-sectional view showing the configuration of thesolder connectors shown in FIG. 19, which are formed in a self-assembledmanner.

FIG. 21A is a top view showing a wire-bonded (WB) state as a prior art,and FIG. 21B is a cross-sectional view taken along a line I-I in FIG.21A.

FIG. 22 is a cross-sectional view showing a conventionalresin-encapsulated body (semiconductor module).

FIG. 23 is a cross-sectional view showing a semiconductor device mountedby a conventional flip chip bonding (FC) method.

FIG. 24 is a cross-sectional view showing a semiconductor device forwhich a conventional tape automated bonding (TAB) method is employed.

FIG. 25 is a cross-sectional view showing the configuration in which aconventional semiconductor device is mounted on a mounting board.

FIGS. 26A to 26C are cross-sectional views illustrating the mechanism bywhich solder connectors are formed in one example of the presentinvention.

DESCRIPTION OF THE INVENTION

In the mounted body according to the present invention, the elementelectrode of the semiconductor element is connected electrically to theelectrode terminal of the wiring pattern formed on the mounting boardvia a solder connector formed of solder particles assembled into abridge shape. The bridge-shaped solder connector is formed by heating asolder resin paste containing the solder particles, a resin, and aconvection additive so that the convection additive boils to causeconvection in the resin, thus causing the solder particles to assembleinto a bridge shape so as to connect the element electrode and theelectrode terminal. That is, the convection additive contained in thepaste boils when heated, which brings about the assembly (hereinafteralso referred to as the “self-assembly”) of the solder particles. Thus,the bridge-shaped solder connector is formed between the electrodes. Ifthe solder particles also are melted at this time, the solder particlesself-assemble at the element electrode and the electrode terminal, whichboth have high solderability, whereby the solder connector can beformed.

Preferably, the mounted body of the present invention further includes afacing substrate on which an electrode pattern is formed, and theelectrode pattern is positioned above the semiconductor element with thesolder connector intervening therebetween. It is preferable that thefacing substrate is a light-transmitting substrate. The reason for thisis that this allows the solder connector to be formed while checking theconnected state thereof visually.

The facing substrate may be a flexible substrate. An opposite surface ofthe facing substrate also may have an electrode pattern. A shieldinglayer may be formed on the opposite surface of the facing substrate.

Furthermore, it is preferable that a recess is formed on a portion ofthe mounting board, and the rear surface of the semiconductor element isin contact with a bottom surface of the recess.

Furthermore, it is preferable that an upper surface of the mountingboard is substantially coplanar with the surface of the semiconductorelement. Still further, it is preferable that the semiconductor elementis a thin semiconductor chip having a thickness of not less than 10 μmand not more than 100 μm. With this configuration, the overall thicknessof the mounted body can be reduced.

It is preferable that the solder connector is embedded in the resin. Theresin corresponds to the resin in the solder resin paste, containing areduced amount of the solder component. It is preferable that this resinalso is a light-transmitting resin. The reason for this is that thisallows the solder connector to be formed while checking the connectedstate thereof visually.

Next, in the method according to the present invention, the facingsubstrate may be removed after the bridge-shaped solder connector hasbeen formed. This allows electrical testing to be performed through theelectrode pattern.

Furthermore, it is preferable that a surface of the element electrode,electrode terminal, or electrode pattern is subjected to a coatingtreatment for improving solderability. This makes the formation of thesolder connector easier. The coating treatment for improving thesolderability refers to a treatment of forming a solder plating, a goldplating, or the like with a thickness of 0.05 to 30 μm, for example.

The solder connector may have a portion extending along the electrodepattern.

The solder resin paste includes a resin, solder particles, and aconvection additive that boils when the resin is heated. A thermosettingresin (e.g., epoxy resin) is used as the resin, and Pb free solderparticles are used as the solder particles. As the convection additive,a solvent (e.g., an organic solvent) can be used, examples of whichinclude isopropyl alcohol (boiling point: 82.4° C.), butyl acetate(boiling point: 125° C. to 126° C.), butyl carbitol (diethylene glycolmonobutyl ether, boiling point: 201.9° C.), and ethylene glycol (boilingpoint: 197.6° C.). The content of the convection additive in the resinis not particularly limited, and preferably is 0.1 to 20 wt %.

Note here that the “convection” of the convection additive meansconvection as a kinetic form, which may be in any form as long as themotion of the boiling convection additive in the solder resin pastegives kinetic energy to the metal particles (the solder particles)dispersed in the resin, thereby promoting the movement of the metalparticles. Note here that, in addition to the convection additive thatboils to cause convection in itself, it is also possible to use aconvection additive that generates gas (gas such as H₂O, CO₂, or N₂)when the resin is heated. Examples of such a convection additive includecompounds containing crystal water, compounds decomposed by beingheated, and foaming agents.

As the solder particles, any solder particles can be selected for use.Examples of the solder particles include those listed in Table 1 below.The materials given as examples in Table 1 can be used alone or in anyappropriate combinations. As the material of the solder particles, it ispreferable to use a material whose melting point is lower than thecuring temperature of the thermosetting resin, because this allows,after the resin has been caused to flow to cause self-assembly of thesolder particles, the resin to be heated further so as to be cured, thusachieving electric connection and encapsulation with the resin.

TABLE 1 Composition of solder particles Melting point (solidus) (° C.)Sn—58Bi 139 Sn—37Pb 183 Sn—9Zn 199 Sn—3.0Ag—0.5Cu 217 Sn—3.5Ag 221Sn—0.7Cu 228 12Sn—2.0Ag—10Sb—Pb 240

The melting point of the solder particles preferably is 100° C. to 300°C., more preferably 139° C. to 240° C. as shown in Table 1. When themelting point is lower than 100° C., the problem concerning thedurability tends to occur. When the melting point is higher than 300°C., the selection of the resin becomes difficult.

The average particle diameter of the solder particles preferably is inthe range from 1 to 30 μm, more preferably from 5 to 20 μm. When theaverage particle diameter is less than 1 μm, it becomes difficult tomelt the solder particles due to the surface oxidation, and theformation of the electric connectors tends to take too much time. Whenthe average particle diameter is more than 30 μm, it becomes difficultto obtain the electric connectors due to the sedimentation of the solderparticles. Note here that the average particle diameter can be measuredusing a commercially available particle size distribution analyzer. Forexample, the average particle diameter can be measured using a laserdiffraction particle size analyzer (LA920) available from HORIBA, Ltd.,a laser diffraction particle size analyzer (SALD2100) available fromShimadzu Corporation, or the like.

Next, the resin will be described. Typical examples of the resininclude: thermosetting resins such as epoxy resin, phenol resin,silicone resin, diallyl phthalate resin, furan resin, and melamineresin; thermoplastic resins such as polyester elastomer, fluororesin,polyimide resin, polyamide resin, and aramid resin; photocurable(ultraviolet curable) resins; and mixtures of at least two kindsthereof.

The mixing ratio by weight of the solder particles and the resinpreferably is in the following range: conductive particles:resin=70 to30:30 to 70, more preferably, solder particles:resin=60 to 40:40 to 60.It is preferable to use the solder particles and the resin after theyhave been mixed together homogenously. For example, 50 wt % of solderparticles and 50 wt % of epoxy resin are mixed homogenously with akneading machine, and a convection additive is added to the resultantmixture to prepare a paste in which the solder particles remaindispersed.

Furthermore, in preferred examples of the present invention, lead-freesolder alloy particles whose melting point is 200° C. to 230° C. can beused as the solder particles, for example. When the resin is athermosetting resin, it is preferable that the curing temperature of theresin is higher than the melting point of the solder. With thisconfiguration, it is possible to cure the resin during the steps offorming electric connectors and forming metal bumps, thus allowing theoperation process to be shortened.

After the solder connector has been formed, it is possible to wash awaythe solder resin paste that is not yet cured, then fill another resin(which may be the same type of resin), and cure this resin. In thiscase, the resin contained in the solder resin paste for forming thesolder connectors is not necessarily a thermosetting resin or aphotocurable resin. Furthermore, in the case where the resin to befilled later is a thermosetting resin, it is preferable that the curingtemperature of the resin is lower than the melting point of the solder.The reason for this is that this prevents the solder connector frombeing deformed again when curing the resin.

According to the present invention, the element electrode of thesemiconductor element is connected electrically to the electrodeterminal of the mounting board via a solder connector formed in aself-assembled manner. Thus, it is possible to provide a novel finepitch connection technique that is different from the wire bonding (WB)method, the flip chip bonding (FC) method, and the tape automatedbonding (TAB) method.

In the following, the mechanism by which solder connectors are formed inone example of the present invention will be described with reference tothe drawings.

First, as shown in FIG. 26A, a solder resin paste 215 containing metalparticles (e.g., solder powder) 212, a convection additive 213, and aresin 214 is supplied onto a circuit board 210 on which a plurality ofconnection terminals 211 are formed. The convection additive 213 boilsto cause convection when the solder resin paste 215 is heated.

Next, as shown in FIG. 26B, a semiconductor chip 220 having a pluralityof electrode terminals 221 is brought into contact with the surface ofthe solder resin paste 215. At this time, the semiconductor chip 220 isarranged so that the electrode terminals 221 thereof face the connectionterminals 211 of the circuit board 210. In this state, the solder resinpaste 215 is heated. The heating temperature of the solder resin paste215 is set to be higher than the melting point of the metal particles212 and the boiling point of the convection additive 213.

The metal particles 212 melted by the heating bind each other in thesolder resin paste 215, and self-assemble between each pair of theconnection terminals 211 and the electrode terminals 221, which bothhave high solderability, as shown in FIG. 26C. Thus, solder connectors222 that electrically connect between the electrode terminals 221 of thesemiconductor chip 220 and the connection terminals 211 of the circuitboard 210 are formed. Thereafter, the resin 214 is cured or solidified,whereby the semiconductor chip 220 is fixed to the circuit board 210.

This technique is characterized in that, when the solder resin paste 215is heated, the convection additive 213 boils to cause convection in thesolder resin paste 215, thereby promoting the movement of the metalparticles 212 dispersed in the solder resin paste 215. Thus, the bindingof the metal particles 212 proceeds uniformly, and the solder connectors(the solder bumps) 222 can be formed in a self-assembled manner. In theabove process, the resin 214 in the solder resin paste 215 is consideredto serve as “sea” in which the metal particles can float and movefreely. However, the binding process of the metal particles 212completes within a very short time. Thus, even if the “sea ” in whichthe metal particles 212 can move freely is provided, the bindingproceeds only locally. Hence, the resin 214 serving as the “sea” and thepromotion of the convection by the convection additive 213 areimportant. By using the resin 214 and the convection additive 213 incombination, the solder bumps 222 are formed in a self-assembled manner.It should be noted here that the solder bumps 222 are formed not only ina self-assembled manner but also in a self-aligned manner due to thenature of the solder bumps.

The inventors of the present invention came up with the above-describedidea and further expanded the idea to finally achieve the presentinvention.

Hereinafter, the present invention will be described by way ofembodiments with reference to the drawings. In the following descriptionas to the drawings, elements having substantially the same functions aregiven the same reference numerals for the sake of simplicity inexplanation. It should be noted that the present invention is by nomeans limited to the following embodiments.

Embodiment 1

First, a mounted body according to an embodiment of the presentinvention will be described with reference to FIG. 1. FIG. 1schematically shows the cross-sectional configuration of a mounted body100 according to the present embodiment.

The mounted body 100 according to the present embodiment includes asemiconductor element 10 having element electrodes 12 and a mountingboard 30 on which wiring patterns 35 each having an electrode terminal32 are formed. The semiconductor element 10 has a surface 10 a on whichthe element electrodes 12 are formed and a rear surface 10 b opposingthe surface 10 a. The rear surface 10 b of the semiconductor element 10is in contact with the mounting board 30. The element electrodes 12 ofthe semiconductor element 10 are connected electrically to the electrodeterminals 32 of the wiring patterns 35 via solder connectors 20 formedin a self-assembled manner. It is to be noted here that the solderconnectors 20 formed in a self-assembled manner are obtained by growingthem on the element electrodes 12 and the electrode terminals 32 througha predetermined process, rather than by preparing solder members asshown in FIG. 1 beforehand and placing them on the element electrodes 12and the electrode terminals 32. The details of the predetermined processwill be given later.

In the present embodiment, the mounted body is configured so that itincludes a substrate 40 on which electrode patterns 42 are formed. Thesubstrate 40 is arranged on the semiconductor element 10 in such amanner that a surface 40 a on which the electrode patterns 42 are formedfaces the surface 10 a of the semiconductor element 10 with a resin 25intervening therebetween. The solder connectors 20 are formed inside theresin 25 while being in contact with the electrode patterns 42 of thesubstrate 40. Preferably, the substrate 40 is a light-transmittingsubstrate, which can be a glass substrate and a light-transmitting resinsubstrate, for example. In the present embodiment, a glass substrate isused as the substrate 40.

The mounting board 30 shown in FIG. 1 is a rigid substrate (a typicalprinted board), and a recess 37 is formed in a portion of the mountingboard 30. The rear surface 10 b of the semiconductor element 10 is incontact with the bottom surface of the recess 37. In this example, anupper surface 30 a of the mounting board 30 and the surface 10 a of thesemiconductor element 10 are substantially coplanar (e.g., ±50 μm) witheach other, and thus, upper surfaces of the element electrodes 12 andupper surfaces of the electrode terminals 32 are substantially at thesame height.

The semiconductor element 10 is a bare chip, for example. The thicknessof the semiconductor element (the bare chip) 10 is 50 to 500 μm, forexample. In the example shown in FIG. 1, the element electrodes 12 arearranged in a peripheral region of the chip surface 10 a (peripheralarrangement). FIG. 2 shows an example of the planar configuration inwhich the semiconductor element 10 having the element electrodes 12employing the peripheral arrangement are connected to the mounting board30 with the solder connectors 20 of the present embodiment.

As shown in FIGS. 1 and 2, the element electrodes 12 of thesemiconductor element 10 are connected electrically to the electrodeterminals 32 via the solder connectors 20. The electrode terminal 32 isformed at one end of each of the wiring patterns 35, and preferably hasa land shape. The solder connector 20 extends upward from the elementelectrode 12. It is formed along the electrode pattern 42 of thesubstrate 40 and reaches the electrode terminal 32. The resin 25 isprovided around the solder connectors 20, and the adjacent solderconnectors 20 are insulated from each other by the resin 25. The solderconnectors 20 are formed in a bridge shape.

The solder connectors 20 are formed in a self-assembled manner. Also,they are formed in a self-aligned manner with respect to the elementelectrodes 12 and the electrode terminals 32. Accordingly, misalignmentof the solder connectors 20 with respect to the element electrodes 12and the electrode terminals 32 does not occur substantially, and thesolder connectors 20 are formed automatically so as to correspond to thepattern of the element electrodes 12 and the electrode terminals 32. Thesolder connector 20 connects the element electrode 12 and the electrodeterminal 32 while taking a bridge shape therebetween.

In the present embodiment, the metal (solder) used for forming thesolder connectors 20 is a low melting point metal, examples of whichinclude Sn—Ag based solders (including those to which Cu or the like hasbeen added). The low melting point metal is not limited to the Sn—Agbased solders (including those to which Cu or the like has been added),and any low melting point metals having a melting point within the rangefrom 100° C. to 300° C. can be used. Besides the Sn—Ag based solders,the solder particles also can be formed of, for example, Pb-free solderssuch as Sn—Zn based solders and Sn—Bi based solders, Pb—Sn eutecticsolders, and low melting point metals such as Cu—Ag alloy. In thepresent embodiment, solder particles formed of an Sn—Ag—Cu material andhaving an average particle diameter of 20 μm were used.

As the resin 25, a thermosetting resin such as epoxy resin was used. Inthe present embodiment, it is preferable that the resin 25 is alight-transmitting resin (e.g., epoxy resin). The thickness of the resin25 (that is, the distance between the chip surface 10 a and the lowersurface 40 a of the substrate 40) is, for example, 500 μm or less, morepreferably not less than 10 μm and not more than 100 μm The resin 25surrounds at least the solder connectors 20, the element electrodes 12,and the electrode patterns 42. The wiring patterns 35 formed on themounting board 30 and the electrode patterns 42 formed on the substrate40 are formed of copper, for example, and they both have a thickness of5 μm to 35 μm, for example.

The connection method according to the present embodiment is a novelconnection method that is different from the above-described wirebonding method, flip chip bonding method, and TAB method, and it hasvarious features and advantages as will be described below.

First, with the configuration of the present embodiment, the rearsurface of the semiconductor element 10 can be arranged on the substrate30. Thus, the semiconductor element 10 can be set in the recess 37 ofthe mounting board 30 by means of die bonding as in the case of the WBmethod. Furthermore, since the rear surface 10 b of the semiconductorelement 10 is in contact with the mounting board 30, favorable heatdissipation can be achieved.

Moreover, the semiconductor element 10 can be connected electrically tothe substrate 30 with the solder connectors 20 formed along theelectrode patterns 42 of the substrate 40. That is, the elementelectrodes 12 and the electrode terminals 32 can be connectedelectrically to each other collectively with the solder connectors 20.In other words, the necessity of connecting them one by one as in the WBmethod is eliminated. Therefore, as compared with the WB method, thetime and effort required for the operation can be reduced. In addition,since the electric connection with the solder connectors 20 can beachieved in a self-assembled manner, it can be performed more easilythan in the WB method as long as the conditions therefor are setproperly. Moreover, a smaller equipment investment is required.Furthermore, since the solder connectors 20 are formed in a self-alignedmanner, the necessity of aligning them with high accuracy at the time ofelectric connection is eliminated and the problem of misalignment due tothe tolerance can be avoided. Thus, the configuration of the presentembodiment is extremely valuable from a technological viewpoint.

In addition, the pitch can be defined by the electrode patterns 42 andthe electrode terminals 32. Thus, as compared with the WB method, theconfiguration of the present embodiment is more suitable for fine pitchconnection. Furthermore, since the solder connectors 20 are formed in aself-assembled manner and in a self-aligned manner as described above,the advantage thereof further increases in the case of such fine pitch.Moreover, as compared with the case where the WB method is employed, themounting area can be reduced.

Moreover, with the configuration of the present embodiment, it ispossible to check the positions of the element electrodes 12 of thesemiconductor element 10 through the substrate 40, so that alignment canbe performed more easily than in the FC method. Furthermore, when theresin 25 is a transparent resin, alignment can be performed easily evenafter the application of a paste made of the transparent resin.Similarly, the electrode terminals 32 on the mounting board 30 also canbe aligned easily. In the case of the FC method, since theelectrode-formed surface 10 a of the semiconductor element 10 faces themounting board 30, it is difficult to check the connection state of thesemiconductor element 10 and the substrate 30 visually. In contrast,with the configuration of the present embodiment, not only the alignmentbut also the checking of the connection can be performed easily. Inaddition, with the configuration of the present embodiment, because thesolder connectors 20 are formed in a self-aligned manner, many problemsconcerning the alignment are avoided inherently.

Moreover, an increase in the cost of the mounting board 30 can besuppressed as compared with the case of the FC method, because it isonly required that the electrode patterns 42 of the substrate 40 a befine patterns. Furthermore, in the case where the semiconductor elementis of the area array-type, a large number of terminals are concentratedin a specific region (i.e., a region of the substrate where thesemiconductor element faces) in the FC method, so that, in many cases,it becomes necessary to increase the number of the layers constitutingthe wiring board. In contrast, with the configuration of the presentembodiment, the routing of the wirings can be achieved by the electrodepatterns 42 of the substrate 40, so that, as compared with the case ofthe FC method, the number of layers of the mounting board 30 can bereduced. This also contributes to the suppression of the increase in thecost of the mounting board 30.

With the configuration of the present embodiment, the surface of thesemiconductor element 10 can be protected with the substrate 40 and theresin 25, and also the connection portion of the semiconductor element10 and/or the connection portion of the mounting board 30 is protected.Thus, excellent connection reliability is achieved. Also, the solderconnectors 20 are protected with the resin 25 and the substrate 40.

In the mounted body 100 according to the present embodiment, it ispossible to use the element electrodes 12 of the semiconductor element10, which are not provided with solder bumps, so that the cost increasecan be suppressed accordingly. In particular, an advanced technique isrequired for the formation of the bumps on the element electrodes 12that include a large number of pins and are arranged with a narrowpitch, resulting in an increase in cost. Thus, the fact that theformation need not be performed is highly advantageous. That is, unlikethe case of the FC method, there is an advantage in that thesemiconductor element 10 can be connected electrically to the mountingboard 30 without forming bumps on the element electrodes 12 beforehand.

In the case of the TAB method, it is necessary to perform an inner leadbonding step and an outer lead bonding step separately. In contrast,with the configuration of the present embodiment, the semiconductorelement 10 and the mounting board 30 are connected electrically to eachother via the solder connectors 20, whose one end and the other end arein contact with the semiconductor element 10 and the mounting board 30,respectively, so that the electric connection can be achieved easily.Furthermore, as compared with the case where the TAB method is employed,the mounting area can be reduced.

Furthermore, in the mounted body 100 shown in FIG. 1, the rear surface10 b of the semiconductor element 10 is in contact with the bottomsurface of the recess 37 formed in the mounting board 30, so that theapparent thickness of the semiconductor element 10 can be zero or can bereduced. Thus, it is possible to make the mounted body 100 thinner.Also, in the present example, the surface 10 a of the semiconductorelement 10 is substantially coplanar with the upper surface 30 a of themounting board 30, so that the solder connectors 20 can be formedrelatively easily. However, as will be described later, even if thesurface 10 a of the semiconductor element 10 is not coplanar with theupper surface 30 a of the mounting board 30, it is still possible toform the solder connectors 20 in a self-assembled manner and aself-aligned manner.

Furthermore, since the upper surface 40 b of the substrate 40 is flat,it is possible to mount electronic components (e.g., chip components)thereon. Moreover, on the upper surface 40 b of the substrate 40, wiringpatterns may be formed, or alternatively, a shielding layer may beformed. The shielding layer can be a solid layer made of a conductivematerial, for example. As described above, the substrate 40 is notlimited to a glass substrate, and other substrates (resin substrates)also can be used. Also, the substrate 40 is not limited to alight-transmitting substrate, and other substrates (e.g., asemiconductor substrate and the like) also can be used.

Next, a method for manufacturing the mounted body 100 according to thepresent embodiment will be described with reference to FIGS. 3A to 3E.FIGS. 3A to 3E are cross-sectional views illustrating major steps in themanufacturing method according to the present embodiment.

First, as shown in FIG. 3A, a semiconductor element (e.g., a bare chip)10 is placed on a mounting board (e.g., a rigid printed board) 30. Inthis example, a recess 37 is formed in the mounting board 30, and thesemiconductor element 10 is arranged so that a bottom surface 10 b ofthe semiconductor element 10 is positioned on a bottom surface of therecess 37. On an upper surface 10 a of the semiconductor element 10,element electrodes 12 are formed. On the other hand, wiring patterns 35including electrode terminals (lands) 32 are formed on an upper surface30 a of the mounting board 30.

Next, as shown in FIG. 3B, a solder resin paste 21 is applied to aregion including the element electrodes 12 and the electrode terminals32. In the present embodiment, the solder resin paste 21 is applied soas to cover the entire electrode-formed surface (the entire uppersurface) 10 a of the semiconductor element 10 and a portion (a portionincluding the electrode terminals 32) of the mounting board 30.

The solder resin paste 21 includes a resin, solder particles (not shown)dispersed in the resin, and a convection additive (not shown) that boilswhen the resin is heated. In the present embodiment, a thermosettingresin (e.g., epoxy resin) is used as the resin, and Pb free solderparticles are used as the solder particles. As the convection additive,a solvent (e.g., an organic solvent) can be used, examples of whichinclude isopropyl alcohol, butyl acetate, butyl carbitol, and ethyleneglycol. The content of the convection additive in the resin is notparticularly limited, and preferably is 0.1 to 20 wt %.

Note here that the “convection” of the convection additive meansconvection as a kinetic form, which may in any form as long as themotion of the boiling convection additive in the resin gives kineticenergy to the metal particles (the solder particles) dispersed in theresin, thereby promoting the movement of the metal particles. Note herethat, in addition to the convection additive that boils to causeconvection in itself, it is also possible to use a convection additivethat generates gas (gas such as H₂O, CO₂, or N₂) when the resin isheated. Examples of such a convection additive include compoundscontaining crystal water, compounds decomposed by being heated, andfoaming agents.

Next, as shown in FIG. 3C, a substrate 40 is placed on the appliedsolder resin paste 21. It is preferable that the substrate 40 is alight-transmitting substrate, and in the present embodiment, a glasssubstrate is used as the substrate 40. Also, it is possible to use aresin substrate or a semiconductor substrate as the substrate 40.Electrode patterns 42 are formed on a lower surface 40 a of thesubstrate 40. A portion of each electrode pattern 42 is positioned aboveat least a portion of the corresponding element electrode 12, andanother portion of the electrode pattern 42 is positioned above at leasta portion of the corresponding electrode terminal 32.

Next, as shown in FIG. 3D, the solder resin paste 21 is heated so thatthe convection additive (not shown) boils to cause convection 27 in theresin. In many cases, vapor bursts out from between the substrate 40 andthe mounting board 30 when the convection additive is boiled. Thisheating process is carried out in such a manner that the temperature atwhich the boiling of the convection additive is caused is equal to orhigher than the melting point of the solder particles. Owing to theconvection 27 caused by the convection additive, the solder particles inthe solder resin paste self-assemble on the element electrodes 12, theelectrode patterns 42, and the electrode terminals 32. Without theconvection 27 (boiling) caused by the convection additive, the growth ofthe solder particles cannot be promoted, so that aggregates (undissolvedlumps) of the solder particles remain.

As the self-assembly of the solder particles proceeds, solder connectors20, each connecting between the element electrode 12 and the electrodepattern 42 and between the electrode terminal 32 and the electrodepattern 42, are formed. In the present embodiment, the solder connector20 has a portion extending along the electrode pattern 42, and theelement electrode 12 and the electrode terminal 32 are connected to eachother directly via the solder connector 20. The time required forforming the solder connectors 20 in FIGS. 3D and 3E is, for example,about 5 to 30 seconds (preferably, about 5 seconds), although this mayvary depending on the conditions under which the solder connectors 20are formed. It is to be noted that the process for forming the solderconnectors 20 may include a preheating step of heating the solder resinpaste 21 beforehand.

The solder connectors 20 are formed by the self-assembly of the solderparticles in the solder resin paste 21. Thus, after the solderconnectors 20 have been formed, the resin included in the solder resinpaste 21 contains substantially no conductive particles, so that theadjacent solder connectors 20 are insulated from each other by the resin25.

It is to be noted that, after the solder connectors 20 have been formed,it is possible to wash away the solder resin paste 21 that is not yetcured, then fill another resin (which may be the same type of resin),and cure this resin. In this case, the resin contained in the solderresin paste 21 for forming the solder connectors 20 is not necessarily athermosetting resin or a photocurable resin. Furthermore, in the casewhere the resin to be filled later is a thermosetting resin, it ispreferable that the curing temperature of the resin is lower than themelting point of the solder. The reason for this is that this preventsthe solder connectors from being deformed again when curing the resin.

The following is a specific example therefor. The solder connectors 20were formed using, as the solder resin paste 21, a mixture obtained byhomogenously mixing 57 parts by weight of transparent epoxy resin (JapanEpoxy Resins Co., Ltd., trade name “Epikote 806”), 40 parts by weight ofthe above-described solder particles, and 3 parts by weight of a solventcomposed of isopropyl alcohol. Thereafter, the solder resin paste 21 waswashed away. Another thermosetting epoxy resin (NAMICS CORPORATION,trade name “8422”) then was filled and cured by heating.

By curing the resin included in the solder resin paste 21 (or anotherresin), the mounted body 100 according to the present embodiment isobtained. In the case where another resin is filled, a resin other thanthermosetting resins (e.g., a thermoplastic resin, a photocurable resin,or the like) can be used as the resin included in the solder resin paste21.

In the case of the FC method, a resin (an underfill material) often isfilled into a space between a semiconductor element and a mountingboard, thus increasing the number of process steps. In contrast,according to the manufacturing method of the present embodiment, thecured resin 25 also can serve as an underfill material, so that it ispossible to avoid the problem of the increase in the number of processsteps.

In the present embodiment, since the light-transmitting substrate isused as the substrate 40, the connection by the solder connectors 20 canbe checked through the substrate 40. Moreover, since thelight-transmitting resin is used as the resin 25, the connection can bechecked still more easily.

Subsequent to the state shown in FIG. 3E, the substrate 40 may beremoved. When the substrate 40 is removed to expose the electrodepatterns 42 or the solder connectors 20 on the upper surface of theresin 25, it becomes possible to conduct electrical testing using theconductive portions thus exposed. For example, electrical testing can beconducted by removing the substrate 40 to expose the electrode patterns42 and bringing a terminal (e.g. a probe) of a tester into contact withthe electrode patterns 42.

Embodiment 2

In a mounted body 100 shown in FIG. 4, a layer 43 for improvingsolderability is formed on a surface of each electrode pattern 42 of asubstrate 40. That is, in this example, the surfaces of the electrodepatterns 42 are subjected to a coating treatment for improvingsolderability. By improving the solderability of the surfaces of theelectrode patterns 42, the formation of solder connectors 20 in aself-assembled manner can be achieved easily or more stably. The coatingtreatment for improving the solderability can be, for example, formationof an SnBi layer as a solder plating layer.

Embodiment 3

In a mounted body 100 shown in FIG. 5, a mask layer 45 is formed on aportion of a surface of each electrode pattern 42, and each solderconnector 20 includes a solder bump portion 20 a connecting an elementelectrode 12 and the electrode pattern 42 and a solder bump portion 20 bconnecting an electrode terminal 32 and the electrode pattern 42. Evenif the solder connector 20 does not connect the element electrode 12 andthe electrode terminal 32 directly, it is possible to connect theelement electrode 12 and the electrode terminal 32 electrically to eachother via the electrode pattern 42 as in this example. The mask layer 45is formed of a material whose solderability is lower than that of theelectrode pattern 42. For example, the mask layer 45 is formed of asolder resist. When the mask layer 45 is formed in such a manner that,on the surface of the electrode pattern 42, it is present on an areabetween a portion corresponding to the element electrode 12 and aportion corresponding to the electrode terminal 32, the solder connector20 is divided into two portions (20 a, 20 b) as shown in FIG. 5. Thiscan bring about an advantage in that the predictability of the shape ofthe solder connector 20 can be improved and thus the properties (theresistance, stress, strength, etc.) of the solder connector 20 can bepredicted easily.

The shape of the solder connector 20 can be changed without forming themask layer 45. In a mounted body 100 shown in FIG. 6A, the shape of anelectrode pattern 42 is devised. For example, as shown in FIG. 6B, theelectrode pattern 42 is designed so that, as compared with areas of aportion 42 a corresponding to an element electrode 12 and a portion 42 bcorresponding to an electrode terminal 32, an area of a portion 42 cconnecting these portions (42 a, 42 b) becomes smaller. With thisconfiguration, during the formation of the solder connectors 20 byself-assembly, the solder connectors 20 are likely to be brought intocontact with the portions 42 a, 42 b first. Also, the joint portion 42 ccan be formed so as to be inclined, as shown in FIG. 6C. Note here that,in accordance with the area of the element electrode 12 and the area ofthe electrode terminal 32, the area of the portion 42 b corresponding tothe electrode terminal 32 is made larger than the area of the portion 42a corresponding to the element electrode 12.

Embodiment 4

In a mounted body 100 shown in FIG. 7, the substrate 40 is removed sothat electrode patterns 42 are exposed on a surface. The removal of thesubstrate 40 can be achieved by separating the substrate 40 or grindingthe substrate 40. Because the electrode patterns 42 are exposed, itbecomes possible to use them as test terminals. Furthermore, a resin 25may be removed from the mounted body 100 shown in FIG. 7, thus providingthe configuration shown in FIG. 8.

Furthermore, as shown in FIG. 9, the electrode patterns 42 can beremoved from the mounted body 100 shown in FIG. 7, thereby exposingsolder connectors 20. The resin 25 may be removed further therefrom,thus providing the configuration shown in FIG. 10.

Embodiment 5

In the mounted bodies 100 shown in FIGS. 8 and 10, the elementelectrodes 12 and the electrode terminals 32 are air-insulated from eachother. However, a resin 25 may be present between the element electrodes12 and the electrode terminals 32 to improve the insulation properties.As shown in FIG. 11, upper surfaces of solder connectors 20 may becurved slightly instead of being flat. This configuration corresponds tothe configuration shown in FIG. 8 modified by being subjected to a heattreatment (e.g., a reflow treatment) for a short time so that the solderconnectors 20 are melted slightly to be deformed into a shape that canrelieve stress more significantly.

Embodiment 6

In a mounted body 100 shown in FIG. 12, a semiconductor element 10 isplaced on a typical mounting board 30 with its upper surface 30 a beingflat.

In this case, in order to reduce the difference in height between uppersurfaces of element electrodes 12 and upper surfaces of electrodeterminals 32 so as to allow the formation of solder connectors 20 in aself-assembled manner to be performed more easily, a thin semiconductorchip preferably is used as the semiconductor element 10. In this case,the thickness of the semiconductor element 10 is 150 μm or less,preferably about 100 μm. Note here that, even when the semiconductorelement 10 has a thickness of more than 150 μm (e.g., about 200 to 450μm), the solder connectors 20 still can be formed in a self-assembledmanner without any problems.

When a substrate 40 is removed from the mounted body shown in FIG. 12, amounted body 100 as shown in FIG. 13 is obtained. When the resin 25further is removed and a reflow treatment or the like is performed sothat the shape of the solder connectors 20 is modified so as to suppressthe stress applied to the solder connectors 20, a mounted body 100 asshown in FIG. 14 is obtained. Note here that, in the configuration shownin FIG. 14, a resin 25 can be provided between element electrodes 12 andelectrode terminals 32.

The mounted body 100 shown in FIG. 12 can be produced in the mannerillustrated in FIGS. 15A to 15E, which is similar to the manner shown inFIGS. 3A to 3E. That is, a semiconductor element first is placed on aflat mounting board 30 as shown in FIG. 15A, and then a solder resinpaste 21 is applied as shown in FIG. 15B. Next, a substrate 40 is placedon the solder resin paste 21 as shown in FIG. 15C, and the solder resinpaste 21 is heated as shown in FIG. 15D. Then, a convection additive(not shown) boils to cause convection 27 in a resin, and theself-assembly of solder particles proceeds. Then, solder connectors 20are formed as shown in FIG. 15E. Thus, the mounted body 100 is obtained.

The mounting board 30 is not limited to a rigid printed board, and canbe a lead frame 30 including a die pad portion 30 b and a lead portion30 a as shown in FIG. 16. Furthermore, as already described above, it isalso possible to use a flexible printed board as the mounting board 30.The upper surface of the substrate 40 need not be flat. For example,using a flexible substrate as the substrate 40, the mounted body may beconfigured so that the upper surface of the substrate 40 is curved asshown in FIG. 17.

Moreover, by using a soft substrate such as a flexible substrate as thesubstrate 40, it is possible to reduce stress applied to the solderconnectors 20, thus stabilizing the connection portions. In addition,the gap between the electrode terminals 32 and the electrode patterns42, which is expanded by the thickness of the semiconductor element 10,can be reduced, so that stable connection can be achieved also at theelectrode terminals 32.

Furthermore, in the configuration example shown in FIG. 2, the elementelectrodes 12 and the electrode terminals 32 are led out such that thespacing (the pitch) between the element electrodes 12 is equal to thatbetween the electrode terminals 32. However, as shown in FIG. 18, afan-out arrangement may be employed in which the spacing (pitch) betweenthe electrode terminals 32 is larger than that between the elementelectrodes 12.

Although the above-described configuration example shows thesemiconductor element 10 in which the element electrodes 12 are arrangedin a peripheral region, the semiconductor element 10 is not limitedthereto. It is also possible to use the semiconductor element 10 inwhich the element electrodes 12 are arranged in an array form. Moreover,the number of terminals of the element electrodes 12 is not particularlylimited, and the technique according to the embodiment of the presentinvention becomes more advantageous as the number of pins is larger andthe pitch is narrower.

Embodiment 7

Next, the state of solder connectors 20 formed in a self-assembledmanner in a mounted body 100 according to the present embodiment will bedescribed with reference to FIGS. 19 and 20.

A cross-sectional micrograph of FIG. 19 shows the cross section of amounted body shown in FIG. 20, which was exposed by actually grindingthe mounted body, observed through a microscope. The mounted body shownin FIG. 20 was obtained by placing a semiconductor element 10 on aflexible substrate 30 provided with a solid copper layer 35′ and thenforming solder connectors 20 connecting element electrodes 12 andelectrode terminal regions 32′ in a resin 25 in a self-assembled mannerthrough the process illustrated in FIGS. 3B to 3E.

As shown in FIG. 19, the solder connector 20 extends upward from theelement electrode 12 and is formed along an electrode pattern 42′ toreach the electrode terminal region 32′ positioned below the electrodepattern 42′. In the cross section shown in FIG. 19, the cross-sectionalconfigurations of the respective elements partially are unclear due tothe influence of an abrasive agent filled therein. The semiconductorelement 10 has a thickness of 100 μm or less (in this example, 50 μm).The substrate 30 and the substrate 40 have a thickness of 30 μm.

The present invention has been described by way of preferredembodiments. It should be noted, however, the present invention is by nomeans limited by the description of these preferred embodiments, andneedless to say, various changes can be made to the present invention.

Although the above-described embodiments of the present invention aredirected to the case where the semiconductor element 10 is a bare chip,the semiconductor element 10 is not limited to a bare chip, and can be asemiconductor package such as a chip size package (CSP), for example.Although it is preferable that the semiconductor element 10 is a memoryIC chip, a logic IC chip, or a system LSI chip, the type of thesemiconductor element 10 is not particularly limited.

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to provide a mountedbody for which a novel fine pitch connection technique that is differentfrom the WB method, the FC method, and the TAB method is employed andalso to provide a method for manufacturing the same.

1. A mounted body comprising: a semiconductor element having a surfaceon which an element electrode is formed and a rear surface opposing saidsurface; and a mounting board on which a wiring pattern having anelectrode terminal is formed, wherein the rear surface of thesemiconductor element is in contact with the mounting board, the elementelectrode of the semiconductor element is connected electrically to theelectrode terminal of the wiring pattern formed on the mounting boardvia a solder connector formed of solder particles assembled into abridge shape, the mounted body further comprises a facing substrate onwhich an electrode pattern is formed, and the electrode pattern ispositioned above the semiconductor element with the solder connectorintervening therebetween.
 2. The mounted body according to claim 1,wherein the facing substrate is a light-transmitting substrate.
 3. Themounted body according to claim 1, wherein the facing substrate is aflexible substrate.
 4. The mounted body according to claim 1, wherein anopposite surface of the facing substrate also has an electrode pattern.5. The mounted body according to claim 1, wherein a shielding layer isformed on an opposite surface of the facing substrate.
 6. The mountedbody according to claim 1, wherein a recess is formed on a portion ofthe mounting board, and the rear surface of the semiconductor element isin contact with a bottom surface of the recess.
 7. The mounted bodyaccording to claim 6, wherein an upper surface of the mounting board issubstantially coplanar with the surface of the semiconductor element. 8.The mounted body according to claim 1, wherein the semiconductor elementis a thin semiconductor chip having a thickness of 100 μm or less. 9.The mounted body according to claim 1, wherein the solder connector isembedded in a resin.
 10. The mounted body according to claim 9, whereinan upper surface of the resin is substantially flat.
 11. The mountedbody according to claim 9, wherein the resin is a light-transmittingresin.
 12. The mounted body according to claim 1, wherein the elementelectrode and the electrode terminal are connected electrically to eachother via the electrode pattern.
 13. A mounted body comprising: asemiconductor element having a surface on which an element electrode isformed and a rear surface opposing said surface; and a mounting board onwhich a wiring pattern having an electrode terminal is formed, whereinthe rear surface of the semiconductor element is in contact with themounting board, the element electrode of the semiconductor element isconnected electrically to the electrode terminal of the wiring patternformed on the mounting board via a solder connector formed of solderparticles assembled into a bridge shape, and the solder connector isformed so as to be in contact with an electrode pattern positioned at anupper surface of the solder connector.
 14. The mounted body according toclaim 13, wherein a recess is formed on a portion of the mounting board,and The rear surface of the semiconductor element is in contact with abottom surface of the recess.
 15. The mounted body according to claim14, wherein an upper surface of the mounting board is substantiallycoplanar with the surface of the semiconductor element.
 16. The mountedbody according to claim 13, wherein the semiconductor element is a thinsemiconductor chip having a thickness of 100 μm or less.
 17. The mountedbody according to claim 13, wherein the solder connector is embedded ina resin.
 18. The mounted body according to claim 17, wherein an uppersurface of the resin is substantially flat.
 19. The mounted bodyaccording to claim 17, wherein the resin is a light-transmitting resin.